Rotogravure printing process



May 21, 1940. A. w. RABY ET AL ROTOGRAVURE PRINTING PROCESS Filed June9, 1938 Patented May 21, 1940 UNITED STATES PATENT OFFICE It. Ilarvey,Cooksvil signors to The Canada le, Ontario, Canada, as- Toronto Star,Toronto, Ontario,

Application June a, 1938,8611! No. 212,012

8 Claims.

This invention relates to the process of preparing a printing surface oncopper surfaced rolls for the reproduction of photographic sub-'- .iectsand the principal objects are to overcome some of the major diiiicultiesmet with in the preparation of the etched surfaces for intaglioprinting, and to produce prints in which the shadow portions will be ofuniform tone.

The principal features of the invention consist in the novel steps inthe process of'creating an intaglio printing surface in which deepshadows are produced having an intaglio reproduction of a combination ofhalf-tone dots and a fine mesh screen, the intersecting lines of thescreen forming a grid surface enclosing a multiplicity of intagliorecesses interspersed between the ordinary half-tone dot recesses.

In the accompanying drawing Figure 1 is an enlarged representationofaportion of a picture illustrating the arrangement of ordinaryhalftone dots on a screened negative.

.Figure 2 is a similar illustration of the arrangement of fineintersecting screen lines on a film positive.

Figure 3 is a representation of a contact film positive produced by acombination of the halftone dot-screen negative and the line screenpositive which is produced in intaglio on the copper plate by etching.

Figure 4 is an enlargeddetail showing the arrangement of half-tone dotsand screen in intaglio.

In carrying this process into effect a continuous tone negative is firstproduced by photographing the object, This negative is suitablyretouched and from this negative is produced a continuous tone positivewhich in turn is suitably retouched. To this point the process is thesame as is practiced in the ordinary gravure process.

A screened half-tone negative is then made from the retouched positiveas illustrated in Figure 1 of the drawing.

A very contrasty negative film print is then made from the retouchedpositive and from this is printed a film positive, with a fine line meshhalftone negative of Figure 1 with the screen shape positive of Figure 2to produce a final positive representation as illustrated in Figure 3 inwhich all tones are represented by halftone dots oi' varying sizesexcept in the deep shadow portions and in such portions there is acombination of half-tone dots and screen.

It will be noted as illustrated in Figure 2 that the screen positive isa fiat or uniform tone and has no influence on the gradation of theimage which is carried by the half-tone dots, but the screen beingsuperimposed on the deep shadow surfaces, forms a bearer surface formedof a combination of dot and line screen.

When the final positive, which is represented by Figure 3, is completedit is placed directly over the copper plate or. cylinder which has beenpreviously prepared with a sensitized coating, and it is then "exposed.to light in the usual manner of producing a resist print, after which itis developed and fixed ready for etching.

The etching is' accomplished in a single operation and produces over theordinary light-tone surfaces an arrangement of intaglio recesses ofvarying sizes to produce the final printing effect of the shaping andgradation of the image and in those places where the fine line screen isinterposed the surface is etched to form a multiplicity of intagliorecesses separated by the fine lines of the screen in the metal betweenthe dot recesses.

It will bereadily understood by those skilled in the art, that wheredeep shadows occur and particularly where such shadows covercomparatively large areas, the body of ink on such areas will be veryeffectively retained against being gouged or wiped out, with the resultthat the ultimate picture produced in the printing will be featured bysolid uniform colour tone, which is the principal objective. Further itwill be readily appreciated that the various steps in achieving thedesired result are of a simple nature ensuring accurate results.

It will also be appreciated that the present process introduces intogravure printing the use of the half-tone screen which, by reason of theouter exposure of paper surface, produces a much more luminous type ofprint and a better working medium which enables a more faithfulreproduction.

What we claim as our invention is:

i. A rotogravure printing process comprising incorporating into aifinalpositive film of the image to be reproduced a combination of halftonedots and screen lines by contact exposure thereof through a superimposedhalf-tone screen I negative and a contrasty continuous tone negative anda transparent line screen so that said positive presents closely spacedscreen lines in theshade areas only of the image, exposing a sensitizedmetal surface through the resultant positive I of the image to bereproduced, developing and finally etching the metal surface.

2. A rotogravure printing process comprising, forming a half-tonenegative by exposure through a half-tone screen, forminga screenlinepositive by exposure of predetermined areas only thereof through agravure screen, and com bining the half-tone negative image with thescreen line positive and reproducing the combined effect thereof on asensitized metal printing surface by the exposure, developing andetching process.

3. A rotogravure printing process comprising first producing acontinuous tone positive and a half-tone screen negative, then from saidcontinuous tone positive producing a contrasty continuous tone negative,then placingsaid continuous tone negative together with a screen havingfine and closely spaced transparent intersecting lines over a sensitizedfilm and exposing the latter therethrough to produce a transparentmedium having light-obstructing screen lines confined to areasrepresenting the shadow portions of the image, then by the contact andexposure method eifecting the transfer of the halftone screen and lineimages respectively of said half-tone screen negative and saidtransparent medium to a transfer medium, and utilizing said transfermedium for the reproduction of the combined half-tone and screen lineeifect on a metal printing surface.

4. A rotogravure printing process comprising first producing acontinuoustone negative, then from the negative producing a positive continuoustone image, then from the positive producing a half-tone screennegative, from the continuous tone positive producing by superimposition'a negative mask having light-penetrable areas corresponding to the darkor shaded areas of said positive, from the mask producing a screen-linepositive by exposure of a light-sensitive layer through a fine linescreen, combining by superimposition the screen line positive andhalf-tone screen negative to produce a positive, placing a lightsensitive coatingon a metal surface, ex-

posing said coating through the said combined half-tone and line screenpositive, and etching the metal surface to produce an intaglio printingplate.

5. A rotogravu're printing process comprising I first producing ahalf-tone screen negative and a continuous tone positive, then from saidcontinuous tone positive producing a contrasty continuous tone negative,then placing said continuous tone negative together with a screen havingfine and closely spaced transparent intersecting lines over a sensitizedfilm and exposing the latter therethrough to produce a transparentmedium having light-obstructing screen lines confined to areasrepresenting the shadow' portions of the image, then by the contact andexposure method producing from said half-tone screen negative and saidtransparent medium a transparent film positive, and then by the contact,exposure and etching method reproducing said positive on a metalprinting surface.

6. A rotogravure printing process comprising,

forming a half-tone negative by exposurethrough a half-tone screen,forming a screenline positive by exposure of predetermined areas onlythereof through a gravure screen, the gravure screen lines of which arespaced more closely than the rows of half-tone dots, and combining thehalf-tone negative image with the screen line positive and reproducingthe combined effect thereof on a sensitized metal printing surface bythe exposure, developing and etching process.

7. A rotogravure printing process comprising, forming a half-tonenegative by exposure through a half-tone screen, forming a screenlinepositive by exposure of predetermined areas only thereof through agravure screen, and combining the half-tone negative image with thescreen line positive with the gravure screen lines acutely intersectingthe rows of half-tone dots and reproducing the combined efiect thereofon a sensitized metal printing surface by the exposure, developing andetching process.

8. A rotogravure printing process comprising, forming a half-tonenegative by exposure througha half-tone screen, forming a screenlinepositive by exposure of predetermined areas only thereof through agravure' screen, the gravure screen lines of which are spaced morecloselythan the rows of half-tone dots, and combining the half-tonenegative image with the screen line positive with the gravure screenlines acutely intersecting the rows of half-tone dots and reproducingthe combined effect thereof on a. sensitized metal printing surface bythe exposure, developing and etching process.

AR'I'HUR W. RABY. GEORGE R. HARVEY.

